Unit 3
Characteristics of Electricity
Unit 3
• Electrical energy has allowed us to develop technologies that
have enhanced our way of life
Hybrid
• Hybrid vehicles are often used today where, one part of the
vehicle uses a gasoline powered motor and also energy from
an electrical motor
• As oil prices continue to rise and the environmental concerns
are addressed, using electricity for transportation will become
even more important
Chapter 7
Static Electricity is produced by
electron transfer
Objectives
By the end of the lesson you should be able to:
• State the 3 Laws of Electrostatics
• Describe a Coulomb
• Describe how a static charge is created, measured and
transferred
• Describe insulators and conductors
Physics Intro
• Physics: the study of energy and its uses
• For this unit we will be focusing on Electrical Energy
Electricity
• Electricity is the study of the electron and its uses
•
•
•
•
Where is electricity used?
Why do we get shocked?
How do light bulbs work?
How does electricity actually flow?
Remember
• An atom has 3 subatomic particles
Proton
Neutron
Electron
• There are positive and negative charges
• Electrons move fairly easily – Proton and neutrons do not!
• Add electrons = negative
• Remove electrons = positive
Electrostatics
• Electrostatics = the study of non-moving electrons
• The Laws of Electrostatics:
• Opposite charges attract
• Like charges repel
• Neutral objects are attracted to any charge
• An induced charge results from the movement of electrons by
charged objects nearby, not by direct contact!
• An electroscope measures the amount of static electricity
Static Charge
• An excess of positive or negative charges that stay in place on
an object for a relatively long period of time.
Examples: Lightning, static cling in clothes, receiving a shock
when touching a door handle
The Coulomb
• Charles Coulomb: lived during the 1700s
• Developed a way to measure the quantity of electrons
• Named the unit the Coulomb (C)
• One C equals 6.24x1018 charges
Since 1 electron = 1 negative charge
1 C = 6.24 x 1018 electrons!!
Did you know
• Lightning contacts the ground at a speed of approximately
220000 km/h
Positive and Negative Charges
• Charles Du Fay (1698 –
1739) discovered two
types of static electric
charges. Benjamin
Franklin (1706 – 1790)
named the two charges
positive (+) and negative
(-) charges.
Chemistry Recap
• Atoms are made up of protons ( +), neutrons
(0), and electrons (-).
• # protons = # electrons, the atom is neutral.
• Electrons orbit the nucleus and move quite
easily.
• Movement or transfer of electrons from one
atom to another changes the charge on the
atom.
A Neutral Atom (Lithium)
Chemistry Recap
• When an atom loses electrons, the atom becomes more
positive.
• When the atom gains electrons, it becomes more negative.
• Neutral objects do not have a charge.
Conductors
• Allow electrons to transfer freely
• Metals are excellent conductors because they can give electrons
easily eg. Copper or aluminum
Insulators
• Materials that do not allow electrons to move easily from one
location on an object to another (electrons tend to stay with
the atom they are attached to).
Examples: glass, plastics, ceramics, dry wood.
Creating Static Electricity
• Friction between two objects causes one object to lose
electrons and the other object to gain electrons
Generating Static Charge
• Friction causes objects to
become charged
• For example, the static
charge in clouds is
produced due to the friction
as hot air rises rapidly in the
cloud banks
• The Van de Graaff generator
uses friction to produce a
large static charge on a
metal dome using a moving
belt
Applications
• Devices in chimneys use static charge to remove small
particles of dust
• Plastic sandwich wrap clings use static electricity
• Air Ionizers clean the air by attracting charged particles in the
air
• Static electricity is used in painting automobiles
Dangers of Static Electricity
• Before pumping fuel you need to get rid of static electricity
because they can cause an explosion
• Allowing charge to flow into Earth’s surface is called grounding
• Lightning rods on houses and large buildings provide a ground
rather than hitting the building